Autobox oil - David Horn

Which is better for a Vauxhall Astra autobox (AF13)? Dexron II or Dexron III? I'm using DII at the moment, changed the oil about 5,000 miles ago. Still a nice pink colour.

Anyway, there's an unpleasant grinding noise which comes from the box on a cold morning (6 degrees or below) which doesn't go away until the car's warmed up. (done it since new, Vauxhall say ignore it if there's no metal in the oil.)

Would using a different type of oil solve this problem?

Thanks in advance!
Autobox oil - Aprilia
Its an Aisan-Warner electronic box. DIII is better (lower viscosity at low temps). I doubt it will solve your problem though.

Value my car